Knee misalignment
A knee misalignment is an axis deviation between the thigh and lower leg . A more precise term is axis misalignment at the knee joint , while a leg axis misalignment can be caused by a knee misalignment , but can also be caused by misalignment of the hip joint, foot, thigh or lower leg bones.
In the front view of the frontal plane , an axial misalignment appears as a bow -leg or genu varum when the lower leg deviates inwards compared to the thigh axis ( varus position ), or as a knock-kneel or genu valgum when the lower leg is compared deviates outwards to the thigh axis ( valgus position ). The result is a one-sided increased strain on the knee joint.
Hyperextension of the knee is a misalignment in the sagittal plane and is known as the genu recurvatum . A rotational malalignment of the knee can be accompanied by axial misalignments; however, it occurs very rarely on its own.
definition
In the normal position, the midpoint of the knee joint lies exactly on the line between the midpoint of the hip joint and the ankle joint ( Mikulicz line ). The angle measured on the outside between the shaft axes of the thigh and the lower leg is approx. 174 °.
- A bow-leg position (a genu varum ) is at a significantly larger angle (from approx. 180 °) (Latin varus = "bent outwards, crooked-legged"). Then the knee lies largely outside the Mikulicz line, see also varus position .
- A knock-kneed position (a genu valgum ) is at a significantly smaller angle (from approx. 171 °) (Latin valgus = "saber-legged"). In this case the knee lies significantly further inward of the Mikulicz line, see also valgus position .
Most of the time, both knee joints have the same deformity. If you look at both legs together, you get the picture of an O or an X. The terms bowlegs and knock knees are therefore preferably used in the plural.
- Axial misalignment of the legs
If one
Normal position
Knock knees
Causes of knock knees
In rickets , a lack of vitamin D disrupts bone structure. The bone does not harden properly and cannot support the body weight. The consequences can be both knock-knees and bow-legs. Hypophosphatasia (or phosphatase deficiency rickets) that is not triggered by a vitamin D deficiency can also lead to a pronounced knock-kneed position.
The polio can cause knock-knees.
Knock knees are rarely congenital. In toddlers, knock knees can be corrected with night splints or a cast.
Consequential damage and possible therapies
The long-term consequence can be premature osteoarthritis of the knee joint ( gonarthrosis ). In the case of a knock knee, the outside of the knee joint is more heavily loaded, i.e. the outer articular cartilage of the thighbone (condyle lateralis femoris) and the outer half of the shin plateau. This can overstrain the outer meniscus and lead to lateral osteoarthritis of the knee . With a bow leg, the inner area of the knee joint is more heavily stressed, especially the inner articular cartilage of the thighbone (condylus medialis femoris) . This can overstrain the inner meniscus and lead to medial gonarthrosis.
In the case of a significant misalignment, an epiphysodesis can be carried out before the end of growth , in which the growth plates are closed prematurely on one side and then the residual growth of the growth plate still open on the other side leads to a compensation of the misalignment. Later, after the growth is complete, a malalignment can be corrected by means of an osteotomy above the articular cartilage of the thigh bone (supracondylar femoral osteotomy) or below the tibial plateau (high tibial head osteotomy) .
If significant osteoarthritis is already present, a repositioning osteotomy is usually no longer performed, but instead a knee joint prosthesis is implanted if indicated . A unicondylar sledge prosthesis is also a good indication in the event of complete unilateral wear, either outside or inside.
Individual evidence
- ^ A b c Simone Waldt, Matthias Eiber, Klaus Wörtler: Measurement methods and classifications in musculoskeletal radiology. Thieme 2011, p. 2 ff.
- ↑ Duden online: varus
- ↑ Duden online: valgus
- ↑ According to Duden online are bow legs and knock-knees even plural words . In fact, the singular is also widely used. For example, the technical dictionary Pschyrembel lists the keywords O-Bein and X-Bein and also uses the singular to explain the Latin terms.
